At least three developments motivate the proposed longitudinal study of frail older persons and their informal caregivers: (1) the continued, rapid expansion of the older adult population, especially the oldest-old; (2) the lack of longitudinal studies examining the development and course of informal caregiving in relation to the older person's changing functional health status; and (3) the usefulness of social network concepts in studying this social phenomenon. The investigators propose a carefully designed five-year study of persons aged 70 and over and their informal caregivers. A mixed mode approach to data gathering will involve three stages: (1) screening and subsequent monitoring by mail of non-frail older persons in the community; (2) surveys (telephone and in-person) of frail older persons; and (3) surveys (telephone and in-person) of a primary informal caregiver as identified by the older person. Based on a recently completed cross-sectional study, the proposed longitudinal study will involve approximately 3400 non-frail individuals, 635 frail individuals and 429 informal caregivers at the outset. The study will yield a wealth of descriptive and epidemiological data on the characteristics of these groups of older persons (permitting comparisons of the very old and the oldest-old), their caregiving networks, and their receipt of informal care and/or formal services. These data can be used to inform health and social policy to facilitate development of formal services to complement and support, not duplicate or replace, informal care.